Berlin 2008 – wissenschaftliches Programm

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BP: Fachverband Biologische Physik

BP 7: Posters I

BP 7.29: Poster

Montag, 25. Februar 2008, 17:00–19:30, Poster A

Functional and structural characterisation of plasmodium falciparum actin-I — •Stefan Schmitz, Munira Grainger, Iwan A.T. Schaap, Simone Harder, Irene T. Ling, Antony A. Holder, and Claudia Veigel — National Institute for Medical Research, London, UK

A novel form of acto-myosin regulation has recently been proposed in which the polymerization of actin filaments regulates various types of apicomplexan motility, including parasite invasion of malaria merozoites into red blood cells of the mammalian host. Although it is difficult to visualize filamentous actin within the parasite, we found that actin is one of the most abundant proteins in the merozoite stage of the Plasmodium falciparum life cycle and that monomeric actin extracted from merozoites could be polymerized in the presence of F-actin stabilizing drugs rhodamine-phalloidin or jasplakinolide. In in-vitro motility assays, the average filament velocity of malaria F-actin over rabbit myosin subfragment HMM was indistinguishable from that of rabbit skeletal actin. However, malaria actin filaments polymerized in presence of rhodamine-phalloidin appeared spot-like in fluorescence microscopy, while rabbit skeletal actin prepared under similar conditions had the usual length of several micrometers. Using electron microscopy we found that Malaria actin filaments were on average only about 100 nm long. In order to resolve structural differences between mammalian and malaria F-actin we investigated both forms using atomic force microscopy and negative stain electron microscopy.